Nonlinear extended state observer-based output feedback stabilization control for uncertain nonlinear half-car active suspension systems

This paper proposes a nonlinear extended state observer-based output feedback stabilization controller for a half-car active suspension system, to overcome factors leading to performance deterioration, such as nonlinearities, parameter uncertainties, unmodeled dynamics, and uncertain external disturbances. Nonlinear extended state observers are first developed to estimate the unmeasurable states and unknown dynamics of heave and pitch motions. Then, finite-time stabilization control laws are synthesized to improve the vehicle body attitude and ride comfort. The proposed control scheme is an improvement over the existing linear extended state observer-based techniques, given its high observation quality and finite-time convergence. From the perspective of practical implementation, the controller is independent of an accurate mathematical model and only requires the measurable output signals. By constructing weighted error and auxiliary state systems, and employing geometric homogeneity theory, the finite-time stability of estimation errors and suspension states is systematically proven within the Lyapunov framework. Furthermore, the zero dynamics stability is analyzed to guarantee the suspension space constraint and road holding. Finally, numerical simulations are conducted on some representative road excitations and the results are compared to the existing solution and passive suspension. The analysis has confirmed the effectiveness and robustness of the proposed control method.